JPS5920634A - Manufacture of urethane foam body - Google Patents

Abstract

PURPOSE:To expedite an increase in the strength of a skeleton, to shorten a time required until the removal from a die, and thereby to manufacture the title foam body with excellent productivity, by heating an urethane foam in an outer shell body after cooling the same for a prescribed time. CONSTITUTION:A molding die 6 consisting of a top force 7 and a bottom force 8 is heated to the temperature of 45+ or -5 deg.C by supplying hot water through a water pipe 10 of the die 6, and then foamable urethane resin is injected into the cavity 9 of the die 6 and foamed and inflated therein to form an urethane foam. About five seconds after a tack-free time passes, cold water of 10+ or -5 deg.C is supplied through the pipe 10 to cool down the foam, and thereby the internal pressure of the foam is lowered early (solid line A). Next, about ten-twenty seconds after a foaming time passes, hot water of 45+ or -5 deg.C is supplied to the pipe 10 to heat the molding die 6. Thereby curing reactions are expedited and thus the strength of the skeleton of the foam is increased early (solid line B).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a urethane foam that can shorten demolding time.

[Technical background of the invention]

For example, an insulated door for a refrigerator is constructed by filling an outer shell made of a door outer panel and an inner door panel with urethane foam, and has conventionally been manufactured as follows. That is, a foamable urethane resin is injected into an outer shell housed in a mold, and then the entire mold is placed in a heating furnace to heat the foamed wonton foam to a temperature suitable for a curing reaction, such as about 45°C. This was maintained for a predetermined period of time, and then the outer shell filled with solidified urethane foam was removed from the mold.

[Problems with background technology]

By the way, when using this type of manufacturing method, the time required from injection of the urethane resin to demolding is generally determined by the internal pressure of the urethane foam and the skeletal strength of the urethane foam that presses it down. That is, the internal pressure of the urethane foam is t'! The skeletal strength is determined mostly by the internal temperature, and tends to gradually increase over time as the hardening reaction progresses.If the skeletal strength is removed from the mold when it approaches the internal pressure, the internal pressure will cause the outer shell to swell and deform. will not occur.

However, in the conventional manufacturing method, the temperature of the urethane foam is maintained at a high temperature for a relatively long time due to the reaction heat due to the curing reaction of the polyurethane resin, so the internal pressure remains high for a relatively long time, resulting in demolding. There was a problem in that it took a long time to complete the process, resulting in poor productivity. However, even if the foamed foam is simply cooled to lower the internal pressure, the curing reaction will be delayed and the skeletal strength will not increase quickly, and it will take a long time to demold the foam. It costs a lot.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a urethane foam that reduces the internal pressure of the foam at an early stage while increasing the skeletal strength, thereby shortening demolding time and providing excellent productivity. There is something to do.

[Summary of the invention]

The present invention cools the urethane foam inside the outer shell at a predetermined time and then heats it at a predetermined time, thereby lowering the temperature of the urethane foam whose reaction has progressed to a predetermined stage to quickly reduce the internal pressure. The urethane foam is then heated to increase the skeleton strength as quickly as possible.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIGS. 1 to M3. First, in Fig. 1, reference numeral 1 indicates an insulating door of a refrigerator made of urethane foam finally obtained, which is made by filling an outer shell 4 consisting of a door outer panel 2 and an inner door panel 3 with urethane foam 5. It is composed of Next, in FIG. 2 showing the manufacturing state of this heat insulating door 1, 6 is a molding die, and this is a mold that is divided into upper and lower parts, consisting of an upper mold 7 and a lower mold 8. A cavity 9 for accommodating the outer shell 4 is formed therein. F0 is the water pipe,
This is buried near the cavities 9 of both the upper and lower molds 7 and 8, and is selectively connected to a hot water supply device and a cold water supply device (not shown).

Now, in the above structure, the outer shell 4 is filled with the urethane foam 5 in the following manner. First, in the state shown in Fig. 2, a hot water supply device is connected to the water pipe 10 of the mold B, and hot water of, for example, 45°C is flowed to maintain the mold 6 and the outer shell 4 at about 45°C. put. Thereafter, a foamable urethane resin is injected into the outer shell body 4 using a urethane resin injection device (not shown). As a result, the urethane resin foams and expands within the outer shell 4 to form a urethane foam, which rapidly spreads over substantially the entire area of the outer shell 4. During this time, since the outer shell 4 is maintained at about 45° C., the filling property of the outer shell 4 is good. In addition, along with this foaming reaction, the urethane foam undergoes a curing reaction and gradually gels, generating reaction heat, causing the temperature of the urethane foam to rise rapidly, and the internal pressure to rise accordingly (see solid line A in Figure 6). . Therefore, about 5 seconds after the new tack-free time (about 55 seconds after injection in this example), in which the urethane foam has sufficiently gelled for 4 lines and the urethane foam surface loses its tackiness, molding is performed. Switch the water pipe 10 of type 6 to the cold water supply device side and flow cold water of about 10°C through the water pipe 10.
The mold 6 is cooled to about 10°C. As a result, the heat of reaction is removed and the urethane foam is cooled, so the maximum temperature of the urethane foam is suppressed to a relatively low level, and therefore the internal pressure of the urethane foam is reduced as shown by the solid line A in Figure 6, when the urethane foam is not cooled. (See the one-dot chain line a in FIG. 3), it starts to decrease earlier. After this, about 10 to 20 seconds after the so-called foam time (in this example, about 90 seconds after injection) has passed, when the bubbles in the urethane foam stop rising.
The water pipe 10 of the mold 6 is connected to the hot water supply device again, and hot water of about 45° C. continues to flow through the water pipe 10 to heat the mold 6. As a result, the urethane foam is heated to about 45°C, which is the most suitable temperature for the curing reaction to proceed, so the curing reaction is accelerated and the curing reaction is accelerated. As shown in B, if the skeletal strength is simply continued cooling without reheating (3rd
(see dotted chain line)), and the embrittlement phenomenon on the urethane foam surface can be suppressed.

In this way, the internal pressure of the urethane foam decreases quickly,
In addition, since the skeletal strength increases quickly, the time from injecting the urethane resin until the skeletal strength becomes approximately equal to the internal pressure (time to point P in Figure 3) is longer than the conventional time (time to point Q). Therefore, the demolding time for taking out the insulated door 1 filled with the urethane foam 5 and solidified from the mold 6 can be shortened compared to the conventional method, which improves productivity. You can improve your performance. By the way, after injecting the urethane resin, the foam is about 45%
In the conventional method of maintaining the temperature at a constant temperature, the demolding time was about 5 minutes, but in this leprosy case, the demolding time was reduced to about 3 minutes. Also,
The temperature at which the outer shell 4 is maintained at a high temperature immediately after injecting the urethane resin and during reheating after cooling is such that if it is 55°C or higher, the filling properties will deteriorate, and if it is 35°C or lower, the surface of the urethane foam will become brittle. The temperature at which the outer shell 4 is cooled is desirably from 20°C or above, causing swelling and deformation after demolding, and below 0°C, the rigidity of the 7-ohm cracked shell deteriorates. Therefore, the temperature is preferably about 10±5°C.

Figure 4 shows a second embodiment of the present invention for continuous production of refrigerator doors.
is a fin conveyor, which is driven intermittently at predetermined time intervals to the left in the figure. Reference numeral 12 designates a number of transfer frames placed on the fin conveyor 11, each of which accommodates a field outer plate 2. 15 is a urethane resin injection device,
This is the transfer frame 1 from the starting end side of the fin conveyor 11.
The injection port P1 is located five locations apart from the injection port P1. Reference numeral 14 denotes a heating chamber constituting the heating port (Pz), which is provided to cover 10 portions of the transfer frame 12 following the injection boat P1, and is supplied with steam inside by a steam generator (not shown). It is heated to a constant temperature of about 45°C. Reference numeral 15 denotes a temperature control chamber provided to cover a portion of the fin conveyor 11 that follows the heating chamber 14, and is maintained at a constant temperature of about 20° C. by, for example, a near conditioner. For example, ten presser jigs 16 are disposed in the heating chamber 14 and the temperature control chamber 15 above the fin conveyor 11, respectively. This holding jig 16 closes the open upper surface of the door outer panel 2 from above. Each of the five presser jigs 16 in the first half of the temperature control chamber 15 is provided with a water pipe therein, and cold water is flowed through the water pipe to maintain the temperature at about 10°C, thereby opening the cooling port Ps. In addition, warm water was poured into the same water pipes for each of the five presser jigs 16 described later, and approximately 45
A reheating pot) P4 is configured to maintain the temperature at ℃. Furthermore, these groups of presser jigs 16 can be moved up and down simultaneously at predetermined time intervals, and when the presser jigs 16 rise, the fin conveyor 11 moves to the left by one transfer frame 12. The holding jig 16 moves the corresponding one pitch, and then the holding jig 16 moves downward to close the open upper surface of the door outer panel 2 again, maintains this state for a predetermined period of time, and then rises again, and the cycle is repeated. ing.

Reference numeral 17 denotes a return conveyor, which is used to return the transfer frame 12 that has reached the end of the fin conveyor 11 to the start end of the fin conveyor 11. 18 is a vertical preheating conveyor disposed inside the hood 19, which connects the second floor of the factory where the manufacturing equipment for the door outer panel 2 is installed and the first floor where the fin conveyor 11 is installed. The manufactured door panels 2 are sequentially transferred to the first floor, and during that time, hot air of, for example, about 6D°C is blown into the hood 19 to heat the door panels 2 to about 50°C.
It preheats the temperature. 20 is a carry-in conveyor for feeding the door outer plate 2 into the preheating conveyor 18, and 21 is a carry-out conveyor for transferring the door outer plate 2 from inside the preheating conveyor 18 to the fin conveyor 11 side.

Next, the operation of the above configuration will be explained. First, the door outer panel 2 is placed on the carry-in conveyor 20 t7 and sent into the preheating conveyor 18. Then, the door outer panels 2 that have been preheated to about 50° C. by the preheating conveyor 18 and sent out by the carry-out conveyor 21 are sequentially stored in the transfer frame 12 on the line conveyor 11.

Then, by driving the fin conveyor 11 to the left,
The transfer frame 12 and the door outer panel 2 reach the injection boat P1,
A predetermined amount of urethane stock solution is injected into the door outer panel 2 by the urethane resin injection device 13 . Thereafter, the door outer panel 2 reaches the heating port P2 in the heating chamber 14, and the urethane resin foams and fills the door outer panel 2.

When the tack-free time of the urethane foam has elapsed, the door outer plate 2 comes out of the heating chamber 14 and reaches the cooling hole (Ps) in the temperature control chamber 15. Here, since the presser jig 16 is cooled to about 10'C, the urethane foam is cooled to about 10C, and the reaction heat of the urethane foam is taken away, causing the internal pressure to decrease. Then, when the foam time of the urethane foam has elapsed, the door outer panel 2 reaches reheating point P4. Here, presser jig 1
6 is heated to about 45°C, the urethane foam is reheated to about 45°C, which accelerates the curing reaction of the urethane foam, prevents the surface from becoming brittle, and reduces the skeletal strength. Thereafter, the door outer panel 2 is taken out from the transfer frame 12 that has left the temperature-controlled room 15, and the door inner panel 6 is attached to the door outer panel 2, thereby completing the heat insulating door 1.

〔Effect of the invention〕

As described above, the present invention can reduce the internal pressure of the urethane foam at an early stage and accelerate the increase in skeletal strength, so it is possible to shorten demolding time and provide a method for producing urethane foam with excellent productivity. Can be provided.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is a partially cutaway perspective view of a heat insulating door of a refrigerator, and FIG. 2 is a longitudinal section of a mold together with an outer shell. 3 and 3 are characteristic diagrams showing the initial characteristics of the urethane resin during foaming, and FIG. 4 is a manufacturing process diagram showing a second embodiment of the present invention. In the figure, 1 is a heat insulating door (urethane foam), 4 is an outer shell, and 5
1 is a urethane foam, 6 is a mold, and 10 is a water passing vibrator. Source: Tokyo Shibaura Electric Co., Ltd.

Claims (1)

[Claims] 1. In a product in which foamable urethane resin is injected into the outer shell to fill the inside with urethane foam, the foam in the outer shell is cooled at a predetermined time and then heated at a predetermined time. A method for producing a urethane foam, characterized by: